1. Field of the Invention
This invention concerns a variable resistor circuit module.
2. Description of the Prior Art
Variable resistor circuit modules have been prepared so far by forming a sliding resistor pattern for variable resistor by printing a thick organic film on a copper foil printed substrate for mounting electronic parts and by disposing structural parts of the variable resistor capable of sliding on the sliding resistor pattern thereby varying the resistance value.
However, since the processing temperature upon forming the sliding resistor pattern on the copper foil printed substrate by printing a thick organic thick film is higher than 200.degree. C., materials for the printed substrate are restricted only to those capable of withstanding such a high temperature. In addition, since the copper foil pattern on the printed substrate suffers from oxidation during the processing step, surface treatment using expensive noble metal such as gold or silver to the copper foil is necessary for preventing the oxidation which, however, increase the production cost.
Further, since the mounting and soldering of electronic parts are made after forming the sliding resistor pattern, the sliding resistor pattern may suffer from the undesirable effects of heat and flux contamination, etc and soldering of the electronic parts to the printed substrate has therefore been limited only to those restricted means, for example, manual soldering or reflow soldering.